1. FIELD
This invention is in the field of vehicle-mounted luggage carriers. It relates in particular to improvements in the type of carrier which has two or more low with each slat a pair of slidable, lockable tie-downs.
2. PRIOR ART
Earlier luggage carriers of the permanently affixed type simply provided an enclosed area of luggage, often with fixed, elevated siderails and with endrails or crossbars that were slidable fore and aft along the siderails. In some cases mechanisms were provided for clamping the slidable endrails at particular positions along the siderails, and in some cases eyelets were provided in the siderails for securing ropes. Examples of these types appear in U.S. Pat. No. 3,554,416, filed in 1968 and issued to Bott in 1971.
By 1970 it was becoming customary to protect the vehicle surface with permanently affixed slats, of shallow cross-section, to support the luggage. Such a construction appears, for example, in U.S. Pat. No. 3,623,642, issued in 1971 to James Stephen.
Some of the slats used for this purpose were made of roll-formed sheet metal. In certain particular roll-formed designs, each slat, viewed in lateral cross-section, consisted of a pair of upstanding outer walls, a pair of upstanding inner walls spaced inward from the outer walls, two substantially horizontal (but sometimes arched) top supporting surfaces spanning the gap between each outer wall and its adjacent inner wall, and a recessed horizontal "web" portion connecting the bottom ends of the two inner walls. The luggage load was supported solely upon the two outer walls of the roll-formed sheet-metal slat, the inner walls being shallower and the "web" being elevated above the vehicle surface or any intermediate plastic or rubber mounting pad. Thus the principle purpose of the two inner walls and intervening web was to give the structure rigidity and style, and permit use of an adhesive-affixed or snap-in plastic trim strip down the recessed center of the slat, between the inner walls. Examples of such pre-1973 support slats were those in general production by the Amco Manufacturing Corporation, of North Hollywood, Calif., and others in use on Ford automobiles.
Commercial popularity later shifted to structures more compatible with the low, streamlined styling of modern vehicles. The upstanding siderails disappeared, and the tie-down function was transferred to the slats--which now extended most of the length of the mounting surface, and were either roll-formed sheet metal or extrusions. With this general design shift came an assortment of drawbacks:
Because the slats were very low and shallow, they were not readily amenable to attachment of cord or rope, so it became necessary to provide tie-downs affixed stationarily or slidably to the slats. (By "tie-down" is meant a loop, eye, hook or similar structure about or through which a rope or the like may be tied, strung or otherwise fastened. By "rope or the like" is meant a rope, cable, chain, strap, webbing, elastic cord, thong, or other elongate, generally but not necessarily nonrigid securing element--whether or not provided with an attached eye, hook or other fastening termination.) Stationary tie-downs proved inconvenient in use. Slidable tie-downs were attached either by means of external tracks or flanges along the top upper edges of the slats, or by making use of the central groove--previously used only for trim strips or other visual effects. One natural way to make use of the groove was to form it with a previously well-known conventional dovetail cross-section, or other comparable well-known retaining cross-section, so that it could hold a complementarily shaped nut slidably captive, and thus provides a slidable attachment for a tie-down. Unfortunately both types of slidable tie-down were incompatible with the snap-in plastic trim strips mentioned earlier. If the tie-downs were connected by means of external tracks, the clamping screws engaged and marred the finish of the trim strips. If the tie-downs were connected by means of shaped nuts which slid in a dovetail or other retaining groove, the trim strip had to be removed to permit sliding of the nuts and tie-downs along the slats.
Elevated crossbars were of course still necessary for certain specialized uses, and it was standard practice to attach these to the slats temporarily by the same or similar sliding elements as used for the tie-downs. This attachment arrangement in general serves a useful purpose, and has found extensive commercial use. However, with the added leverage of the crossbars the clamping mechanisms holding the tie-downs to the slats could work loose, permitting the crossbars to slide along the slats--and this in turn could lead to damage of the retaining nuts, the slats, or even the vehicle top or luggage.
Representative of this generation of carriers are U.S. Pats. Nos. 4,015,760 and 4,099,658, both to Bott, issued in 1977 and 1978 respectively, and 4,132,335, which issued in 1979 to Ingram. Some features of the last two patents mentioned represent efforts to resolve some of the drawbacks mentioned, but because of more solid or more elaborate construction these features are objectionably costly.